Cerulo
A section of abyssal plain making up the floor of The Cerulean Trench, Cerulo is the shallowest portion of the trench's crushing depth, but at four thousand, five hundred and six feet, the water pressure would still kill most anything on Tellus.
Cerulo is notable in that it is a natural air pocket and protective area under the surface of the floor of the trench. It is reachable by air breathers through labyrinthine passageways in the walls of the canyon, and the merfolk of the Upper Reaches saw fit to take strategic advantage of such a gift.
Using the cermaic material that their people had been building with for centuries, the merfolk of Cerulo slowly built out a city of formidable size and infrastructure above and around the air pocket that they call home. The people will still retreat there if the city is in danger from some external threat.
Geography
A subterranean air pocket located in a section of bedrock, with an improbable airway linking it to the surface of Tellus.
Localized Phenomena
The air pocket itself is something of a phenomenon. There is a thousands-of-miles-long passage that exchanges air within, making it safe for the merfolk to live there.
Fauna & Flora
Only fauna with very specialized adaptations live this deep, and even those are few and far between out here on the abyssal plain, far from the safety offered by the trench's sides.
Type
Chasm, Underwater
Location under
Owner/Ruler
Ruling/Owning Rank
Owning Organization